Micromechanical sensors, such as accelerometers for sensing acceleration and gyroscopes for sensing rotational rate, often include a proof mass suspended over a support substrate by one or more posts and flexures. The proof mass is responsive to an input, such as inertial acceleration or rotational rate, for deflecting out of a predetermined plane as a result of the Coriolis or acceleration forces induced by the input. One or more sense electrodes sense the out-of-plane deflection of the proof mass for further processing to provide a sensor output signal indicative of the input. One type of sense electrode employs capacitive sensing.
The support substrate over which the proof mass is suspended typically comprises a dielectric, such as silicon or glass. U.S. Pat. No. 5,205,171 to O'Brien et al. describes a micromechanical device in which a proof mass is disposed between, and anodically bonded to, a pair of glass layers.